The present invention relates to gas venting means for venting gases evolved by a liquid enclosed inside a container.
Certain liquids can present storage problems because they evolve substantially insoluble gases, such as oxygen, on prolonged storage. For example, the useful broad-spectrum disinfectant peracetic acid is often stored as a concentrate containing 10 to 20% w/v hydrogen peroxide and 5 to 50% w/v acetic acid in water. Gradual evolution of oxygen due to the slow decomposition of hydrogen peroxide on storage can result in an unacceptable build-up of pressure in sealed containers filled with this peracetic acid concentrate. Therefore, some means is needed to vent gases from such containers without allowing the escape of any liquid from the container, and without allowing contamination of the liquid inside the container from the environment. Moreover, the gas venting means should be able to resist corrosive liquids, such as peracetic acid, and should preferably be simple and inexpensive.
Conventional gas venting means include pressure release valves and membranes that rupture when a predetermined pressure is reached inside the container. The pressure release valves are complex, expensive, and contain metal parts that will corrode in the presence of liquids such as peracetic acid. The rupture membranes suffer from the drawback that, once the membrane has ruptured, liquid can escape from the container and environmental contaminants can enter the container through the ruptured membrane.
GB-A-1529798 describes a venting insert adapted to fit in a container entrance which can be closed by a detachable cover, the insert being adapted to vent gas from the container when the gas pressure exceeds a predetermined level. The insert includes at least one passage passing through it to allow fluids to be dispensed from the open container, and sealing means adapted to form with the cover a fluid-tight seal for the container. However, the sealing is yieldable to allow gas to escape from the passage to the atmosphere when the container gas pressure exceeds a predetermined level. This arrangement can be regarded as a type of pressure release valve. The drawback of this arrangement is that there is nothing to prevent liquid from inside the container being vented to the atmosphere, particularly if the container is inverted so that the venting insert is submerged in the liquid inside the container. Clearly, venting of the liquid from inside the container is undesirable, particularly if the liquid is a corrosive liquid such as peracetic acid.
GB-A-2203730 describes a venting cap for containers used to store volatile liquids. The cap contains a vent covered by first and second hydrophobic porous membranes. As a result, when the container is in an upright position and the cap is fixed, gases from inside the container can vent through the first and second hydrophobic porous membranes to the atmosphere. A drawback of the arrangement described in GB-A-2203730 is that the venting of gases from inside the container is prevented when the container is inverted. Hence, excessive build-up of gases inside the container is still possible with this venting cap.
EP-A-0453434 describes a gas venting outlet for a container used to store a viscous liquid which gives off a low-pressure gas by chemical reaction. The gas outlet consists of a cylindrical sleeve which projects into the container from the underside of the lid, with a hole through the lid in the centre of the sleeve. Inside the sleeve there is a second cylinder, with its solid base uppermost, and made of a resilient plastic material. The interior surface sleeve is provided with a helical groove. A helical channel is thereby defined between the outside surface of the second cylinder and the interior surface of the sleeve. Gas, but not liquid, can escape from the container through this helical channel. Clearly, this gas venting arrangement is not suitable for liquids of low viscosity, since liquids of low viscosity could vent along the spiral channel. Moreover, this venting arrangement would not be suitable if the container is tipped or inverted so as to immerse the gas outlet in the liquid.